Expression help needed please

[flakester]

Howdy all.

I have modeled a shopping trolley. This much I am pleased with.
I have managed to sort out the expression for the rolling of each wheel, via the Relativity: Dr Wheel Rotator. I'm pretty happy with that also.

What I am looking for, is help with understanding the required expression for each castor, to have it rotate correctly as concerns its 'own' direction of travel in relation to the trolley, so that I only have to animate the trolley translation and rotation.... and let the dark art of code take care of the rest, rather than keyframing each castor by hand.

Some would call it lazy - but I'd like to get my knowledge of expressions to a better level than it is currently. This may be difficult seeing as I'm no real friend of maths.

Three of the castors carry keyframed animation at the moment (through parental nulls (Front_Right_Target_Master)... that sort of thing), the other was left blank in my [quite frankly, naff] attempts in figuring out the needed mystical letters and numbers.

If anyone would be kind enough to take a look at the attached scene and maybe offer some info - I'd be most grateful.

Cheers,

flakester.

[flakester]

No worries folk.

Got it sorted, had an uncommon moment of clarity while following the better half around a supermarket today... strangely - with a shopping trolley!
The theory that hit me while staring blankly down the dairy aisle, seems to be holding up so far.

I only animate the position and rotation of the main body of the trolley, and the direction of the castors looks after itself. Start frame and end frame are a little k00kie, but otherwise - all is dandy.

A low quality WMV in a ZIP is attached of the outcome, proof of concept like.


flakester.